What to Expect From a Professional Bottom Paint Job

When Summer Dance got beat up in a freak storm back in 2014, the damage was mainly in two areas. The worst damage was the deck rim and the rub rail, for which I described the repairs in Storm damage repairs. The collateral damage was the bottom paint, which also got hammered as you can see in the following picture. In some areas, the top layer of paint was knocked off and exposed an underlying layer of paint. In other areas, it was knocked off completely down to the fiberglass. It all needed fixed, so it was included in the insurance claim that I submitted. Our insurance company promptly paid the claim so that meant that I wouldn’t have to do all the work!

BEFORE - Just some of the damaged bottom paint
BEFORE – Example of some of the damaged bottom paint

I took Summer Dance to Rod Tomsha of Custom Fiberglass, who recommended a complete refurbishing of the bottom paint. His shop would first remove all the old bottom paint down to the gelcoat. Then they would apply a barrier coat of Interlux Interprotect 2000E , a two-part epoxy primer to seal the hull below the waterline from absorbing moisture and blistering. They would top that off with a new coat of Interlux VC 17m Extra with Biolux, a thin, smooth, hard film, anti-fouling paint.

The hard part

Getting the layers of old bottom paint off wasn’t easy. It took two men two full days of power sanding starting with 40 grit and working up to 320 grit as recommended by Interlux. The paint came off in a fine powder, so full coveralls, eye protection, a respirator, and good ventilation were a must.

Removing the old paint is a grueling, dirty job
Removing the old paint is a grueling, dirty job

Along the way, they discovered places where blistering had begun in the gelcoat. These were all sanded smooth before the barrier coat was applied.

Small blisters in the bottom paint
The many white dots are small blisters in the gelcoat

The easy part

After they had the hard work of sanding the hull done, applying the new bottom coatings was relatively easy. First on was four coats of gray Interlux Interprotect 2000e epoxy primer. After mixing the catalyst into the paint, they rolled it on with a short knap roller after waiting for the previous coat to dry.

Masking the boot stripe after removing a sling
Masking the boot stripe after removing a sling

About an hour after the last coat of primer, they started applying the blue Interlux VC 17m Extra with Biolux. After mixing in the powdered copper that comes with each can, it turns a bronze color.

Interlux VC 17m after mixing
Blue Interlux VC 17m before mixing (left) and after mixing (right)

They rolled on two coats of VC 17m, the recommended starting layer for fresh water, which dries very quickly and requires almost no drying time between coats.

Applying bottom paint over the barrier coat
Applying bottom paint over the barrier coat

The VC 17m stays a bronze color until it has been immersed in water for several weeks and turns blue. When fresh, it looks like a new penny and coordinated well with the dark brown cove stripe and boot stripe.

Closeup of bottom paint below the boot stripe before removing the masking tape
Closeup of bottom paint below the boot stripe before removing the masking tape

However, I chose the blue VC 17m color because I was going to paint the cove and boot stripes dark blue later. That makeover transformed Summer Dance from 80’s brown to classic blue. I had already replaced the brown, tan, and gold cushion covers with blue Sunbrella and made a matching mainsail cover, foredeck bag, engine cover, and bimini.

Closeup of bottom paint below the new boot stripe after four years in fresh water

This bottom paint job was the silver lining in the storm clouds that landed Summer Dance in the shop. Even before the damage occurred, I foresaw needing to do this job myself over a winter together along with refinishing the keel. Thankfully, I only had to refinish the keel at my cost, which presented its own challenges that you can read about at the previous linked article.

This bottom paint job lasted about five years in fresh water before it started wearing a little thin at the edges due to me scrubbing the waterline several times per year to remove tannin stains. I have recoated it once since then, which was an easy DIY job. Performance-wise, I didn’t notice any increase in top speed but I did notice a difference at low speed. Summer Dance moves easier and faster in light breezes than before, which is helpful for both cruising and for racing. I’m very satisfied with the results and I’d do it again.

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11 Comments Add yours

  1. Kirbygalassi@gmail.com says:

    Hello I have a 84 c-22 in the middle of sanding the old coat off. I still have not decided on the paint to use. My worry on the anti fowling paint is does the boat being on a trailer and not in the water soften the paint and cause for it to flake off more. Being a trailer boat, does the frequent on and off the trailer where through the bottom coat where the bunks hit. Now you have had the anti-fowling paint for some time, would you go with a more original fit such as a gel coat. I’m on the fence what is your taking on this?

    1. Hi, Kirby

      The boat being on the trailer when you’re not sailing will extend the life of the paint, not the other way around. Ablative paints are formulated to gradually wash off by the action of the water passing over hull, whether by sailing, tides, or just gently rocking in a slip from marina activity.

      Plus, the more time your boat spends in the water, the more time slime, algae, barnacles, and other organisms have to build up on the paint and require cleaning off, which takes off some of the paint even in fresh water, but to a lesser degree.

      As for bunk wear, if your trailer bunks have any kind of anti-chafe covering, be it carpet, fire hose, or something else and if you launch your boat properly, that is by floating it on and off the trailer and not dragging it up the bunks like a power boat, then you won’t notice any extra wear where the bunks contact the hull.

      The VC17 paint that I have on Summer Dance now is MUCH smoother and low-friction compared to the previous paint. So much so that the boat shifting around a little on the bunks when I tow it is a concern. I can land her on the trailer perfectly centered with the keel between its rollers and space on both sides then, when I get her home, she’s slid over against the rollers on one side or the other. That didn’t happen with the high-build, high-friction ablative paint that was on it before. But I do like this paint better. My boat is faster, looks better, and the paint doesn’t rub off on everything. I’d still choose it if I had to do it over again.

      That doesn’t necessarily mean it’s the right paint for your boat. That depends on how often you sail, whether you race, what kind of water you have, your climate, and so on. I recommend you research what paint is popular among the experienced skippers in your area. Also check the latest paint test results published by Practical Sailor magazine. They do comprehensive, multi-year testing of the major brands and recommend the best long-term performers . The formulas change from year to year to satisfy EPA requirements, market conditions, and new research so it pays to know what you’re getting.

      I’d only suggest you consider not applying an ablative bottom paint if you only occasionally trailer sail and will be strict about washing the bottom regularly. In that case, you could get by with just a barrier coat followed by a one or two-part polyurethane made for under water applications. But if you later decided to keep her in a slip, then you should add an ablative bottom paint.

      As for gel coat, you’ll find it underneath all your old paint if you sand deep enough, but I don’t recommend going that deep if you don’t have to. You might wind up removing a useful epoxy paint barrier coat that you’ll want to replace before you apply bottom paint. But if you discover blisters under the paint, you should repair them first.

      I hope that answers your questions. Thanks for asking and good luck with your bottom paint job. It’s a big messy job but you’ll be glad you did it.

      1. Kirby galassi says:

        Thanks for the reply, after doing much research on bottom paints for the gulf coast I decided to go with Pettit 4700 epoxy primer 3 coats and pettit unepoxy hard antifouling paint… After removing all the previous owners sloppy job with sanding priming and painting the boat looks great with its new shoes. Also added a zinc to the keel to stop the corrosive demons leaking in gulf waters.. Thanks for the advice. The primer cost was 100 gal and paint 85 a gal so was able to do a fairly cheap job compared to most antifouling paints… The sweat equity cost was sky high as it was a lot of work.. Save a buck or two but lost a pound or two in the process.. Sail on sailor

      2. Sounds like you did it the stingy sailor way, Kirby. I hope it lasts forever for ya!

  2. Vin says:

    Q: It sounds like you had a small amount of blistering.. aka pox? I have a 1979 j/24, in which the bottom has lots of little pimples. I haven’t committed her to one-design racing, but I’d like fix it.. sadly, I hear it’s pretty laborious and can involve using a device to “plane off” a thin layer of epoxy, slicing the blisters in the process, then building it back up. $8k-$10k to have someone do it. Eek. Did you give any special consideration to your blisters?

    1. I do have a small area of minor blisters but they’re only aesthetic. If yours are larger than dimes and cover much of the hull, and you want your hull to be perfect, then you may need to resort to such an extensive repair as you describe. But in my opinion, that boat isn’t worth that big of an investment unless it’s already one of a kind, you can easily spare the cost, and you race at a very high level. You could buy two more J24s for that much. Many, many older fiberglass sailboats have some blistering if they’ve spent a significant amount of time in the water. Otherwise, either ignore them or when you strip the hull next time, use a die grinder or Dremel tool to open up each one, let them drain completely, fair them 4-5 diameters larger to the surrounding surface, wash them out with Acetone, let the hull dry completely, then fair the hull with marine filler and repaint. It’s a lot of work for very little payback.

  3. David T. asked this question on an unrelated page. I moved it here since it’s about bottom paint. -$tingy

    I recently purchased a 1985 Oday 23 and it has ablative bottom paint from the previous owners who kept her in the water at a marina. My plan is to keep her basically on the trailer when not in use and I was thinking that a hard bottom paint would be in my best interest over the long term. Recognizing the cost of removal and repainting, do you think that this would be a worthwhile investment?

    1. David,
      If the current paint is in good condition, I would wait until it needs to be replaced before considering switching to a hard bottom paint. I prefer hard paint to soft because it doesn’t rub off on everything that touches it, which is an advantage when you’re trailer sailing. I also noticed a slight speed increase in light winds after switching. But I also sail only in fresh water so an ablative paint might work better in salt water.

      If you’re only going to trailer sail and not leave your boat in the water, I would consider removing all of the bottom paint and leave the hull bare if it’s in good shape. If it’s in not so good shape, I’d consider applying a two-part epoxy barrier coat and/or fresh gel coat but no ablative bottom paint. If you’re going to leave it in the water for months at a time, especially in salt water, then it’s kind of a toss up between hard and soft bottom paint. Soft will be less expensive and less work. Hard will be the opposite but perform better.

      And as they say, you’re mileage may vary depending on the quality of the water you sail in, how often you sail, and paint brand.

      I realize this isn’t a definitive answer but I hope it helps.

      1. David T says:

        Thanks for the informed opinion! The bottom paint is good to finish out this season but I thought this would be at the top of my winter “to do” list . It’s fairly worn and some small bare spots here and there which is why I’m trying to decide my next steps. Right now only using in fresh water but hope to be sailing in brackish to salt eventually. I think the hard paint would be the right choice for me.
        Thanks again!

  4. Douglas says:

    I’m wanting to paint my 84′ Catalina 22 with Interlux 2000E and then VC 17m. It looks like you used about a quart of each for just the keel. How much did you need for the hull? If you know how much per coat that would be very helpful. I plan to do 3 coats of 2000E barrier coat, followed by 2 coats of VC 17m. Thanks for your blog it’s very helpful.

    1. The keel alone didn’t take that much VC 17m. It goes on pretty thin. Since I didn’t buy the bottom paint, I don’t recall how much the shop used but I want to say 5 quarts. Contact Interlux, they might be able to give you a better estimate.

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